Geologists know the climate changes but sadly it seems politicians and the press are more willing to trust the results of incomplete computer models. Climate models are useful but while they are in an early stage of development its best to take a skeptical view of their output.

Thursday, February 12, 2009

Land clearing to blame for extreme weather conditions.

Global warming activists such as Tim Flannery and Clive Hamilton wasted no time this week in blaming the extreme weather conditions that caused a heat wave and helped turn Victoria’s bushfires into a fire storm solely on increased levels of carbon dioxide. However research at the University of Queensland led by Dr Clive McAlpine demonstrates that 150 years of land clearing has also contributed to the warming and drying of eastern Australia leading to increases in temperature and decreasing humidity.

In an Australian first, they applied the CSIRO Mark 3 climate model, satellite data and the DNRW supercomputer, and showed that 150 years of land clearing added significantly to the warming and drying of eastern Australia.

“Our work shows that the 2002-03 El Nino drought in eastern Australia was on average two degrees Centigrade hotter because of vegetation clearing. Based on this research, it would be fair to say that the current drought has been made worse by past clearing of native vegetation. Our findings highlight that it is too simplistic to attribute climate change purely to greenhouse gases. Protection and restoration of Australia's native vegetation needs to be a critical consideration in mitigating climate change.” Dr McAlpine said.

Australian native vegetation holds more moisture, than broadacre crops and improved pastures, and this moisture evaporates and recycles back as rainfall and also helps raise humidity. It also reflects less shortwave solar radiation into space, and this process keeps the surface temperature cooler and aids cloud formation.

As high pressure systems slowly pass the southern part of the continent over summer, the air they draw down from the north, passing over cleared land, has been getting hotter and dryer and helps explain this summer’s heat wave. It also may help explain why these bushfires were so intense, probably more intense than those of Black Friday in 1939 and Ash Wednesday in 1983.

Models show eastern Australia was between 0.4 and two degrees warmer, and south-west WA was between 0.4 and 0.8 degrees warmer. My interpretation of these model outputs suggests that most of the warming in South East Australia over the last 50 years could be explained by land clearing alone. In my opinion this does not appear to leave much warming that can be attributed to CO2 in Australia and raises questions about sensitivity of CO2 computations used in other climate models.

Reducing the chances of future extreme weather events then does not depend solely on reducing CO2 emissions but also in restoring vegetation to critical parts of New South Wales and Queensland. Ironically while clearing of vegetation in bushfire areas is required to reduce the intensity of wildfires, restoring native vegetation in central New South Wales and southern Queensland is also required to reduce the intensity of weather events that create the conditions for wild fires in the first place.

Use of CO2 as a scapegoat for extreme weather events has blinded us from looking for other influences on regional climate systems, its time we opened our eyes to other factors that are affecting our weather. The simplistic picture painted by Hamilton and Flannery simply isn’t correct, it is a complex problem with no simple answer or solution. Perhaps they are spending too much time jet setting the climate change conference circuit and need to spend more time in th elibrary.

The views in the article are those of the author. While Dr McAlpine was made aware of this article he may not necessarily agree with all of it. The author recommends Dr McAlpine be consulted for more detailed information about the role of land clearing on climate change in Australia.